Carvacrol inhibits the progression of oral submucous fibrosis via downregulation of PVT1/miR-20a-5p-mediated pyroptosis.

Oral submucous fibrosis (OSF) is a precancerous condition in the oral cavity, which is closely related to the myofibroblast conversion of buccal mucosal fibroblasts (BMFs) after chronic consumption of areca nut. Emerging evidence suggests pyroptosis, a form of programmed cell death that is mediated by inflammasome, is implicated in persistent myofibroblast activation and fibrosis. Besides, numerous studies have demonstrated the effects of non-coding RNAs on pyroptosis and myofibroblast activities. Herein, we aimed to target key long non-coding RNA PVT1 with natural compound, carvacrol, to alleviate pyroptosis and myofibroblast activation in OSF. We first identified PVT1 was downregulated in the carvacrol-treated fBMFs and then demonstrated that myofibroblast features and expression of pyroptosis makers were all reduced in response to carvacrol treatment. Subsequently, we analysed the expression of PVT1 and found that PVT1 was aberrantly upregulated in OSF specimens and positively correlated with several fibrosis markers. After revealing the suppressive effects of carvacrol on myofibroblast characterisitcs and pyroptosis were mediated by repression of PVT1, we then explored the potential mechanisms. Our data showed that PVT1 may serve as a sponge of microRNA(miR)-20a to mitigate the myofibroblast activation and pyroptosis. Altogether, these findings indicated that the anti-fibrosis effects of carvacrol merit consideration and may be due to the attenuation of pyroptosis and myofibroblast activation by targeting the PVT1/miR-20a axis.

Parameters to assess the necessity of adjuvant therapy for early-stage oral squamous cell carcinoma.

OBJECTIVE: One-third of head and neck squamous cell carcinomas are early-stage oral cavity squamous cell carcinomas (OCSCC). Despite a high curative rate, 20% of early-stage OCSCC patients do not achieve long-term survival. This study evaluates the role of adjuvant therapy (ADJ) in delaying disease progression and prolonging survival. METHODS: This single-institute retrospective cohort study enrolled 481 early-stage OCSCC patients, 16% (78/481) of whom received ADJ. It was reported according to the STROBE guidelines. Cox proportional hazards regression and Kaplan-Meier survival curves were employed to identify suitable candidates for ADJ. RESULTS: The 5-year locoregional recurrence-free survival (LR-RFS) and overall survival rates were 73.2% and 84.9%, respectively. Positive margins and advanced depth of invasion (DOI) were independent predictors of LR-RFS. For patients with positive margins, adjuvant chemoradiotherapy (CRT) was superior to adjuvant radiotherapy alone in improving LR-RFS (hazard ratios for adjuvant CRT vs. none, 0.042; adjuvant radiotherapy alone vs. none, 0.702). Excluding positive margins, advanced DOI was the most critical factor in assessing the need for ADJ. Positive margins and advanced DOI were more appropriate criteria than EORTC 22931/RTOG 9501 for evaluating adjuvant CRT. CONCLUSIONS: Adjuvant CRT was indicated for patients with positive margins and advanced DOI to improve survival outcomes.

Radiomic biomarkers for platinum-refractory head and neck cancer in the era of immunotherapy.

OBJECTIVE: Immune checkpoint inhibitors (ICI) are recommended as the first-line therapy for platinum-refractory head and neck squamous cell carcinoma (HNSCC), a disease with a poor prognosis. However, biomarkers in this situation are rare. The objective was to identify radiomic features-associated biomarkers to guide the prognosis and treatment opinions in the era of ICI. METHODS: A total of 31 platinum-refractory HNSCC patients were retrospectively enrolled. Of these, 65.5% (20/31) received ICI-based therapy and 35.5% (11/31) did not. Radiomic features of the primary site at the onset of recurrent metastatic (R/M) status were extracted. Prognostic and predictive radiomic biomarkers were analysed. RESULTS: The median overall survival from R/M status (R/M OS) was 9.6 months. Grey-level co-occurrence matrix-associated texture features were the most important in identifying the patients with or without 9-month R/M death. A radiomic risk-stratification model was established and equally separated the patients into high-, intermittent- and lower-risk groups (1-year R/M death rate, 100.0% vs. 70.8% vs. 27.1%, p = 0.001). Short-run high grey-level emphasis (SRHGE) was more suitable than programmed death ligand 1 (PD-L1) expression in selecting whether patients received ICI-based therapy. CONCLUSIONS: Radiomic features were effective prognostic and predictive biomarkers. Future studies are warranted.

Is OLP potentially malignant? A clue from ZNF582 methylation.

OBJECTIVE: Whether oral lichen planus (OLP) was potentially malignant remains controversial. Here, we examined associations of ZNF582 methylation (ZNF582m ) with OLP lesions, dysplastic features and squamous cell carcinoma (OSCC). MATERIALS AND METHODS: This is a case-control study. ZNF582m was evaluated in both lesion and adjacent normal sites of 42 dysplasia, 90 OSCC and 43 OLP patients, whereas ZNF582m was evaluated only in one mucosal site of 45 normal controls. High-risk habits affecting ZNF582m such as betel nut chewing and cigarette smoking were also compared in those groups. RESULTS: OLP lesions showed significantly lower ZNF582m than those of dysplasia and OSCC. At adjacent normal mucosa, ZNF582m increased from patients of OLP, dysplasia, to OSCC. In addition, ZNF582m at adjacent normal sites in OLP patients was comparable to normal mucosa in control group. Dysplasia/OSCC patients with high-risk habits exhibited significantly higher ZNF582m than those without high-risk habits. However, ZNF582m in OLP patients was not affected by those high-risk habits. CONCLUSIONS: OLP is unlikely to be potentially malignant based on ZNF582m levels. ZNF582m may also be a potential biomarker for distinguishing OLP from true dysplastic features and OSCC, and for monitoring the malignant transformation of OLP, potentially malignant disorders with dysplastic features and OSCC.

[The Health-Seeking Experience of Patients With Sjögren's Syndrome].

BACKGROUND: The multiple symptoms of Sjögren's syndrome lead patients affected by this disease to seek medical advice from different medical disciplines and specialists. Diagnoses are often made many years after initial onset, resulting in mental and physical exhaustion and misunderstandings. PURPOSE: This study was designed to explore the health-seeking experiences of patients with Sjögren's syndrome. METHODS: Qualitative research methods and purposive sampling were used. Fourteen patients with Sjögren's syndrome were interviewed by the first author, and the collected data were analyzed using content analysis. RESULTS: Four themes were revealed from the data, including: (1) distressing symptoms; (2) difficulty in diagnosis; (3) concerns about drug side effects; and (4) facing the disease. The participants initially sought medical attention when they began experiencing early onset symptoms that caused discomfort or annoyance. Their doctors' failure to provide proper diagnoses during the long health-seeking process caused a great deal of suffering to the participants. Although related medications should be taken for life, the participants reported taking lower-than-prescribed dosages out of fear of side-effects. The participants explored their process of coping with the disease, which began with denial and ended with acceptance. By learning from their health-seeking process, participants realized that they needed to take proper care of themselves, adapt to life with their disease, and control related symptoms. CONCLUSIONS / IMPLICATIONS FOR PRACTICE: To facilitate the early diagnosis of Sjögren's syndrome, healthcare professionals should improve their awareness of this condition and refer patients with related symptoms to rheumatologists and immunologists. Effective early diagnosis and treatment can help these patients reduce the time and effort involved in unproductive doctor's visits, allowing them to better continue as productive members of society and to maintain a good quality of life.

Magnolol inhibits cancer stemness and IL-6/Stat3 signaling in oral carcinomas.

BACKGROUND/PURPOSE: Cancer stem cells (CSCs) have been known to be implicated in tumorigenesis, metastasis, and drug resistance in oral squamous cell carcinomas (OSCC). In this study, we aimed to investigate whether magnolol, a polyphenolic component derived from Magnolia officinalis, exhibited the anti-CSCs properties. METHODS: The cytotoxicity of magnolol was tested using normal gingival epithelioid SG cells and sphere-forming OSCC-CSCs isolated from SAS, OECM1, and GNM cells. Secondary sphere-forming ability, the proportion of ALDH1 positive cells, Transwell migration, and invasion capacities were examined as well. The chemosensitive effects of magnolol were investigated using MTT, secondary sphere-forming, and invasion assays. RESULTS: Magnolol exerted a higher cytotoxicity of OSCC-CSCs and cancer stemness features, including self-renewal ability, the expression CSC marker, migration, and invasion capacities were all downregulated in magnolol-treated OSCC-CSCs. Moreover, administration of magnolol potentiated the effect of cisplatin, including a decrease in cell viability, self-renewal, and invasion activities. In addition, we observed that the secretion of IL-6 and phosphorylation of Stat3 were decreased in OSCC-CSCs treated with magnolol. CONCLUSION: Our data suggest that magnolol is able to target CSCs and suppress the cancer stemness properties, at least in part, via IL-6/Stat3 signaling. Besides, a dietary supplement of magnolol may function as an adjunct to cisplatin treatment.

Oral microbial dysbiosis and its performance in predicting oral cancer.

Dysbiosis of oral microbiome may dictate the progression of oral squamous cell carcinoma (OSCC). Yet, the composition of oral microbiome fluctuates by saliva and distinct sites of oral cavity and is affected by risky behaviors (smoking, drinking and betel quid chewing) and individuals' oral health condition. To characterize the disturbances in the oral microbial population mainly due to oral tumorigenicity, we profiled the bacteria within the surface of OSCC lesion and its contralateral normal tissue from discovery (n = 74) and validation (n = 42) cohorts of male patients with cancers of the buccal mucosa. Significant alterations in the bacterial diversity and relative abundance of specific oral microbiota (most profoundly, an enrichment for genus Fusobacterium and the loss of genus Streptococcus in the tumor sites) were identified. Functional prediction of oral microbiome shown that microbial genes related to the metabolism of terpenoids and polyketides were differentially enriched between the control and tumor groups, indicating a functional role of oral microbiome in formulating a tumor microenvironment via attenuated biosynthesis of secondary metabolites with anti-cancer effects. Furthermore, the vast majority of microbial signatures detected in the discovery cohort was generalized well to the independent validation cohort, and the clinical validity of these OSCC-associated microbes was observed and successfully replicated. Overall, our analyses reveal signatures (a profusion of Fusobacterium nucleatum CTI-2 and a decrease in Streptococcus pneumoniae) and functions (decreased production of tumor-suppressive metabolites) of oral microbiota related to oral cancer.

LncRNA MEG3 inhibits self-renewal and invasion abilities of oral cancer stem cells by sponging miR-421.

BACKGROUND/PURPOSE: Oral cancer stem cells (CSCs) have been considered as the key cells that are implicated in tumor recurrence and metastasis. In recent years, great attention has been paid to the significance of various non-coding RNAs due to their regulatory roles in oral CSCs. Although the function of long non-coding RNA MEG3 in various cancers has been investigated, its effects on the features of oral CSCs remained to be determined. METHODS: The expression levels of MEG3 in tongue squamous cell carcinomas and prognostic effect have been evaluated. We assessed the expression of MEG3 in sphere cells (oral CSCs) using qRT-PCR. Secondary sphere formation and invasion assays were conducted to evaluate the self-renewal and metastatic abilities, respectively. Bioinformatics software and luciferase reporter assay were used to predict and verify the relationship between MEG3 and miR-421. RESULTS: MEG3 was downregulated in the tissues of oral cancer and associated with a poor prognosis. In oral CSCs, the expression of MEG3 was repressed and overexpression of MEG3 resulted in suppression of self-renewal and invasion abilities. Luciferase reporter assay showed that miR-421 directly interacted with MEG3, and our subsequent experiment demonstrated that elevation of miR-421 reversed the MEG3-inhibited characteristics of oral CSCs. CONCLUSION: Our findings suggest that MEG3 can serve as a tumor suppressor in oral CSCs by impeding the action of miR-421. Moreover, targeting MEG3-miR-421 axis has the potential to mitigate the tumor recurrence and metastasis.

Silencing periostin inhibits myofibroblast transdifferentiation of fibrotic buccal mucosal fibroblasts.

BACKGROUND/PURPOSE: Oral submucous fibrosis (OSF) a well-recognized oral premalignant disorder. Several studies have demonstrated that periostin, a matricellular protein, is involved in the development and pathogenesis of fibrosis diseases. Nevertheless, the contribution of periostin in OSF remains to be uncovered. The purpose of the study was to illustrate the functional role of periostin involved in OSF pathogenesis. METHODS: RNA-sequencing was employed to screen for differentially expressed genes in normal and OSF tissues. Validation of the upregulation of periostin in OSF specimens and fibrotic buccal mucosal fibroblasts (fBMFs) was conducted by qRT-PCR. The correlation of the gene expression of periostin and various fibrosis markers was analyzed. In addition, the functional role of periostin in myofibroblast features was tested using collagen gel contraction and transwell migration assays. RESULTS: We observed overexpression of periostin in OSF specimens using RNA-sequencing and confirmed its upregulation in OSF tissues and patient-derived fBMFs. Besides, there was a positive relationship between the expression of periostin and several fibrosis-associated markers, including ACTA2 (α-smooth muscle actin; α-SMA), COL1A1 (type 1 collagen α1 chain), TGFB1 (TGF-ß1), and FN1 (fibronectin). Furthermore, we examined the effect of silencing periostin on the maintenance of myofibroblast characteristics and showed that knockdown of periostin suppressed the expression of α-SMA. Also, inhibition of periostin markedly downregulated the myofibroblast activities (collagen gel contraction and migration capacities). CONCLUSION: Our results indicate the aberrant expression of periostin in OSF tissues and myofibroblasts. Moreover, the expression of periostin is positively associated with fibrosis markers, and repression of periostin may be a promising direction to alleviate the progression of OSF.

Slug mediates myofibroblastic differentiation to promote fibrogenesis in buccal mucosa.

Epithelial-mesenchymal transition (EMT) has been implicated in fibrogenesis and carcinogenesis; however, the exact role of EMT-inducer Slug in the progression of precancerous oral submucous fibrosis (OSF) has not been investigated. In the current study, we showed that the expression of Slug was upregulated in OSF tissues and associated with various myofibroblast markers. After silence of Slug in fibrotic buccal mucosal fibroblasts (fBMFs), the elevated myofibroblast activities and fibrosis markers were all downregulated. Our data revealed that arecoline, an areca nut alkaloid, increased the expression of Slug in normal BMFs, and inhibition of Slug successfully prevented the arecoline-induced myofibroblast activation. Additionally, overexpression of Slug in BMFs stimulated the activities of myofibroblasts, indicating that upregulation of Slug by arecoline contributes to the myofibroblast transdifferentiation. Most importantly, Slug was able to bind to the E-box of type I collagen, leading to increased expression of type I collagen. Altogether, this study demonstrated the abnormal elevation of Slug in OSF and its significance in arecoline-induced fibrogenesis. Moreover, downregulation of Slug could be a potential target for OSF remedy via suppression of myofibroblast activities and type I collagen.

Arctigenin Reduces Myofibroblast Activities in Oral Submucous Fibrosis by LINC00974 Inhibition.

Oral submucous fibrosis (OSF) is an oral precancerous condition associated with the habit of areca nut chewing and the TGF-ß pathway. Currently, there is no curative treatment to completely heal OSF, and it is imperative to alleviate patients' symptoms and prevent it from undergoing malignant transformation. Arctigenin, a lignan extracted from Arctium lappa, has been reported to have a variety of pharmacological activities, including anti-fibrosis. In the present study, we examined the effect of arctigenin on the cell proliferation of buccal mucosal fibroblasts (BMFs) and fibrotic BMFs (fBMFs), followed by assessment of myofibroblast activities. We found that arctigenin was able to abolish the arecoline-induced collagen gel contractility, migration, invasion, and wound healing capacities of BMFs and downregulate the myofibroblast characteristics of fBMFs in a dose-dependent manner. Most importantly, the production of TGF-ß in fBMFs was reduced after exposure to arctigenin, along with the suppression of p-Smad2, α-smooth muscle actin, and type I collagen A1. In addition, arctigenin was shown to diminish the expression of LINC00974, which has been proven to activate TGF-ß/Smad signaling for oral fibrogenesis. Taken together, we demonstrated that arctigenin may act as a suitable adjunct therapy for OSF.

Let-7c restores radiosensitivity and chemosensitivity and impairs stemness in oral cancer cells through inhibiting interleukin-8.

BACKGROUND: The let-7 family of microRNAs has been considered as tumor suppressors in various cancers; however, the role of let-7c in oral squamous cell carcinoma has not been determined yet. METHODS: In this study, phenotypical behaviors and the radio/chemoresistance were examined subsequent to overexpression of let-7c. In addition, the expression of let-7c in cancer stem cells (CSCs) was evaluated and the effect of let-7c on stemness characteristics was assessed. Also, luciferase activity assays were performed to test whether interleukin (IL)-8 was a putative target of let-7c. RESULTS: Our results confirmed that the expression of let-7c in CSCs was reduced, while overexpression of let-7c attenuated the oncogenicity. Moreover, ectopic expression of let-7c in CSCs downregulated the stemness hallmarks and the radio/chemoresistance. Expression and secretion of IL-8 in oral CSCs were both reduced following overexpression of let-7c. Besides, the inhibitory effect of let-7c on various stemness phenotypes was reverted by IL-8, indicating that lower expression of let-7c may confer higher cancer stemness through a failure to downregulate IL-8. CONCLUSION: These findings revealed the significance of let-7c in the contribution of oral cancer stemness and radio/chemoresistance. Targeting let-7c and its downstream IL-8 may be beneficial to prevent cancer recurrence and metastasis of oral squamous cell carcinoma.

miR-200c inhibits the arecoline-associated myofibroblastic transdifferentiation in buccal mucosal fibroblasts.

BACKGROUND/PURPOSE: MicroRNA-200c (miR-200c) recently emerged as an important regulator of tumorigenesis and cancer metastasis, however, its role in regulating oral submucous fibrosis (OSF) remains unknown. In this study, we investigated the functional role of miR-200c in myofibroblastic differentiation activity and identified its potential target. METHODS: qRT-PCR was applied to assess the expression of miR-200c in OSF tissues and fibrotic buccal mucosal fibroblasts (fBMFs). Arecoline, a major areca nut alkaloid, was utilized to explore whether the expression of miR-200c would alter following stimulation. Collagen gel contraction, migration and invasion capabilities were examined in arecoline-stimulated BMFs as wells as in fBMFs. Luciferase reporter assay was conducted to show the relationship between miR-200c and ZEB1. RESULTS: Our results showed that the expression of miR-200c was downregulated in OSF specimen and fBMFs. Arecoline treatment dose-dependently reduced the relative expression of miR-200c in normal BMFs. Overexpression of miR-200c impeded the arecoline-induced collagen gel contraction, migration, invasion and wound healing capacities. Moreover, ectopic expression of miR-200c in fBMFs successfully reduced the increased collagen gel contractility and invasion abilities. Our results demonstrated that ZEB1 was a direct target of miR-200c, and overexpression of miR-200c inhibited the expression of ZEB1 and α-SMA. CONCLUSION: These findings suggest that downregulation of miR-200c in OSF may be involved in the pathogenesis of areca nut-associated OSF through regulation of ZEB1.

LncRNA GAS5-AS1 inhibits myofibroblasts activities in oral submucous fibrosis.

BACKGROUND/PURPOSE: Emerging research findings suggest that long non-coding RNAs (lncRNAs) are key regulators to fibrosis formation. Nevertheless, the role of lncRNA GAS5-AS1 in the progression of precancerous oral submucous fibrosis (OSF) remains to be elucidated. METHODS: Quantitative real-time PCR were used to examine the expression of GAS5-AS1 in OSF tissues. The activities of myofibroblasts, including collagen contractility and cell migration, as well as the marker α-smooth muscle actin (SMA) were assessed following overexpression of GAS5-AS1. Also, we analyzed the expression of Smad activity in order to gain insight into the downstream regulator. RESULTS: The level of GAS5-AS1 was found significantly downregulated in the OSF tissues and fibrotic buccal mucosal fibroblasts (fBMFs). Ectopic expression of GAS5-AS1 significantly reduced the abilities of collagen gel contraction and migration in fBMFs or arecoline-treated BMFs. Moreover, we have shown that overexpression of GAS5-AS1 inhibited the expression of p-Smad and the marker of myofibroblasts. CONCLUSION: We showed the reduced expression of GAS5-AS1 in OSF tissues and demonstrated its effect on the myofibroblast activities and the level of p-Smad and α-SMA, indicating its potential contribution in OSF pathogenesis.

Downregulation of miR-1 enhances tumorigenicity and invasiveness in oral squamous cell carcinomas.

BACKGROUND/PURPOSE: Cumulative evidence suggest that microRNAs (miRNAs) function as biosignatures of oral squamous cell carcinomas (OSCC). However, the functional roles of miR-1 as well as its downstream targets in the regulation of tumorigenicity in OSCC remain unclear. METHODS: miRNAs RT-PCR analysis was performed to identify miR-1 as a putative candidate on mediating invasiveness of OSCC cells. Consequently, we elucidated the tumorigenicity of OSCC cells with miR-1 downregulation or overexpression, respectively. Finally, miR-1 on OSCC tumor tissues was examined. RESULTS: miR-1 levels were significantly downregulated in the malignant OSCC cells. Overexpression of miR-1 significantly reduced migration/invasiveness of OSCC cells. In addition, overexpression of miR-1 decreased cancer stem cells properties. Conversely, downregulation of miR-1 promotes migration and invasiveness in OSCC cells. We have shown that miR-1 is able to target Slug, suppressing their expression. Clinically, lower miR-1 expression was found in patients with advanced nodal metastasis OSCC. CONCLUSION: miR-1 as novel biosignatures in OSCC lymph node metastatic patients, supporting the development of novel strategies for OSCC treatment.

Sulforaphane targets cancer stemness and tumor initiating properties in oral squamous cell carcinomas via miR-200c induction.

BACKGROUND/PURPOSE: Cancer stem cells (CSCs) are deemed as the driving force of tumorigenesis in oral squamous cell carcinomas (OSCCs). In this study, we investigated the chemotherapeutic effect of sulforaphane, a dietary component from broccoli sprouts, on targeting OSCC-CSCs. METHODS: The effect of sulforaphane on normal oral epithelial cells (SG) and sphere-forming OSCC-CSCs isolated from SAS and GNM cells was examined. ALDH1 activity and CD44 positivity of OSCC-CSCs with sulforaphane treatment was assessed by flow cytometry analysis. In vitro and in vivo tumorigenicity assays of OSCC-CSCs with sulforaphane treatment were presented. RESULTS: We observed that the sulforaphane dose-dependently eliminated the proliferation rate of OSCC-CSCs, whereas the inhibition on SG cells proliferation was limited. Cancer stemness properties including self-renewal, CD44 positivity, and ALDH1 activity were also decreased in OSCC-CSCs with different doses of sulforaphane treatment. Moreover, sulforaphane treatment of OSCC-CSCs decreased the migration, invasion, clonogenicity, and in vivo tumorigenicity of xenograghts. Sulforaphane treatment resulted in a dose-dependent increase in the levels of tumor suppressive miR200c. CONCLUSION: These lines of evidence suggest that sulforaphane can suppress the cancer stemness and tumor-initiating properties in OSCC-CSCs both in vitro and in vivo.

Elevation of Twist expression by arecoline contributes to the pathogenesis of oral submucous fibrosis.

BACKGROUND/PURPOSE: Oral submucous fibrosis (OSF), a chronic progressive scarring disease, has been considered as a precancerous condition of oral mucosa. In this study, we investigated the functional role of Twist, an epithelial-mesenchymal transition (EMT) transcriptional factor, in myofibroblastic differentiation activity of OSF. METHODS: Arecoline, a major areca nut alkaloid, was used to explore whether expression of Twist could be changed dose-dependently in human primary buccal mucosal fibroblasts (BMFs). Collagen gel contraction and migration capability in arecoline-stimulated BMFs and primary oral submucous fibrosis-derived fibroblasts (OSFs) with Twist knockdown was presented. RESULTS: We observed that the treatment of arecoline dose-dependently increased Twist expression transcript and protein levels in BMFs. The myofibroblast activity including collagen gel contraction and migration capability also induced by arecoline, while knockdown of Twist reversed these phenomena. Importantly, inhibition of Twist led to the suppression collagen contraction and wound healing capability of primary cultivated OSFs. Clinically, Twist transcript and protein expression was higher in areca quid chewing-associated OSF tissues than in normal oral mucosa tissues. CONCLUSION: This evidence suggests that upregulation of Twist might be involved in the pathogenesis of areca quid-associated OSF through dysregulation of myofibroblast activity.

Chemotherapeutic effects of luteolin on radio-sensitivity enhancement and interleukin-6/signal transducer and activator of transcription 3 signaling repression of oral cancer stem cells.

BACKGROUND/PURPOSE: Previously, we successfully identified oral cancer stem cells (OCSC) displaying enhanced stemness and tumorigenic potentials. In the study, we investigated the chemotherapeutic effect of the flavonoid luteolin, commonly found in fruits and vegetables, on targeting OCSC. METHODS: Oralspheres was applied to isolate OCSC. aldehyde dehydrogenase 1 activity and CD44 positivity of OCSC with luteolin treatment were assessed by flow cytometry analysis. Radio-sensitivity of OCSC treated with luteolin was examined. Invasion and colony-forming assays were performed to assess oncogenicity in OCSC. The expression of interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) was examined by enzyme-linked immunosorbent assay and western blot analysis. RESULTS: We showed that luteolin effectively inhibited the proliferation rate, self-renewal, aldehyde dehydrogenase 1 activity, and CD44 positivity of OCSC but did not cause significant cytotoxicity of normal epithelial cells. Moreover, luteolin restored radio-sensitivity in OCSC. Combined treatment with luteolin and radiation displayed synergistic effect on invasiveness and clonogenicity of OCSC. Mechanistically, treatment of luteolin resulted in inactivation of IL-6/STAT3 signaling. CONCLUSION: These results suggest that combined treatment of luteolin and radiation therapy can attenuate tumorigenicity of OCSC through IL-6/STAT3 signaling inactivation.